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In order to determine what environmental contaminants may be a concern, ATSDR has evaluated
all of the available environmental monitoring data (1986 to present). Comparison values were
used as a basis for evaluation of the data and to determine which contaminants should be looked
at more closely. Comparison values are health-based thresholds below which no known or
anticipated adverse effect on the health of persons should occur. The values allow an adequate
margin of safety. The comparison values used for each contaminant are identified in the
contaminant tables (Tables 1 - 3) found in this section. Appendix 2 contains a description of the
comparison values used in this public health assessment.

A contaminant is selected for further evaluation if the contaminant in a valid environmental
sample exceeds comparison values. The presence of a contaminant on the list in the tables of this
section does not mean that either exposure to the contaminant or adverse health effects has
occurred or will occur. Inclusion in the lists indicates only that the potential for human
exposures to the selected contaminants and the potential for adverse human health effects as a
result of any exposures to the selected contaminants will be discussed in more detail in later
sections of this Public Health Assessment.

As discussed previously, an extensive environmental sampling program has been conducted at
the proposed Potter Company NPL site. This sampling has delineated the extent of soil and
groundwater contamination. The analytical results of the sampling program (1986-1990) are presented in
Table 1.

* - See Appendix 2 for a description of the comparison values and their sources.1 - ND is nondetect.µg/kg - micrograms of contaminant per kilogram of soilµg/l - micrograms of contaminant per liter of water
The bold indicates those contaminants whose concentrations are above the comparison value.

PCBs

PCB (primarily Aroclor 1254) surface soil (top three inches of soil) and subsurface soil
contamination were found at the locations where waste fluids (mixtures of TCE and PCBs) were
reported to have been discharged (See Appendix 1, Figure 1) (1,8). The highest surface soil
contamination was found on the east side of the frame storage building (Area 1). It has been
reported that waste fluids from the degreasing operation (previously located in the frame storage
building) were deposited directly onto the ground at this location. Waste fluids were also
discharged onto the ground at the north-side of the manufacturing building (Area 3). Elevated
levels of PCBs were also detected at this location.

After being discharged onto the ground, the waste fluids and contaminated surface soil (via
surface water runoff - rain) moved downhill towards and into the ditch at the southern part of the
Potter Company property (3). Analytical results of samples taken from these natural drainage
areas indicated that PCB surface soil contamination existed at these locations (Areas 2 and 5).
The waste fluids and contaminated surface soil also moved onto the former Byrd property
(purchased by Potter Company in 1988). Analytical results of samples taken at the former Byrd
property indicate PCB surface soil contamination upwards of 3,300 micrograms of contaminant
per kilogram of soil (µg/kg or ppb) and subsurface soil contamination upwards of 4,700 µg/kg.
The health comparison value (ingestion) for PCBs in soil is 90 µg/kg.

Because PCBs tend to stick or absorb very strongly to soils, PCBs normally do not move very
deeply underground (10). However, the ability for PCBs to move deeper underground is greatly
enhanced in the presence of organic solvents (e.g., TCE and TCA)(9). Therefore, it is possible
the PCB surface soil contamination at the proposed Potter NPL site could have migrated into the
groundwater. In 1987 and 1988, a limited number of groundwater samples (nine) were analyzed
for PCBs. The results of the chemical analysis indicates PCBs are not present in the groundwater
above the detection limits (0.05 µg/l or ppb). However, most of the samples analyzed for PCBs
(eight) were taken from the southern most on-site groundwater monitoring wells (MW-36 and
MW-38, see Appendix 1, Figure 2 for the locations of the monitoring wells). Only one
groundwater sample from the area of highest groundwater contamination was analyzed for PCBs
(MW-35). Additional sampling results from the areas of high groundwater contamination are
needed to confirm that PCBs have not migrated into the groundwater.

All of the PCB soil contamination greater than 10,000 µg/kg (10 ppm) at the Potter Company
property and greater than 1,000 µg/kg (1 ppm) at the former Byrd property and in the drainage
ditch was removed by the remedial activities conducted by Potter in 1988 (2).

TCE and TCA

TCE and TCA were dumped onto the ground along with the PCBs (1). Both TCE and TCA tend
not to adhere very well to soils (11,12). Therefore, they tend to either volatilize (evaporate) into
the air or migrate down through the soil. Analytical results of surface and subsurface soil
samples indicate no significant (not above health comparison values) contamination of TCE,
TCA, or any of their biological breakdown products (i.e., naturally occurring bacteria in soils
tend to change TCE and TCA into 1,2-dichloroethane, 1,1-dichloroethylene, and
trans-1,2-dichloroethylene).

In addition to discharging waste fluids directly onto the ground, waste fluids were also
discharged to the septic systems formerly used by Potter (see Appendix 1, Figure 1 for locations)
(1). Analytical results of subsurface soil and septic tank sludge samples indicate PCBs (up to
4,600 µg/kg), TCE (up to 850 µg/kg), and TCA (up to 91 µg/kg) were discharged at these
locations.

Analytical results of groundwater samples taken from the on-site groundwater monitoring wells
(1988-1990) clearly indicate the groundwater is contaminated with TCE, TCA, and their
biological breakdown products (6). The highest TCE [26,000 micrograms of contaminant per
liter of water (µg/l or ppb)] and TCA (480 µg/l) groundwater contamination was found in the
monitoring well (MW-35B) next to the area where the degreasing fluids were dumped onto the
ground. The highest concentration of TCE and TCA biological breakdown products was found
in the monitoring well (MW-27) nearest the abandoned septic tank next to the metal warehouse.

Table 2 presents the results of the environmental monitoring program conducted in the
surrounding community near the proposed Potter Company NPL site. Surface soil samples were
taken in the unnamed stream. Groundwater samples were collected from the groundwater
monitoring wells installed by contractors working for the Potter Company.

Analytical results of the surface soil samples taken in the unnamed stream indicate PCB
contamination upwards of 103,800 µg/kg (1,4,8). The highest concentration of PCBs were found
right next to the Potter Company property line. The surface soil PCB contamination above 1,000
µg/kg (1 ppm) in and next to the unnamed stream was removed by the Potter Company.

Analytical results from the groundwater samples taken from the monitoring wells clearly indicate
that TCE, TCA, and their biological breakdown products have moved off the Potter Company
property (6). The groundwater contaminants have entered the three water-bearing zones
underlying Wesson. In general, the highest concentration of contaminants have been found close
to the Potter property. Appendix 1, Figure 2 delineates the total extent of groundwater
contamination by TCE above the detection limit of 0.5 ppb in the deeper groundwater zones.

- ENVIRONMENTAL CONTAMINANTS DETECTED ABOVE HEALTH
COMPARISON VALUES IN THE SURROUNDING COMMUNITY NEAR THE
PROPOSED POTTER COMPANY NATIONAL PRIOITIES LIST SITE (1,6,8)

Contaminant

Range in
Surface Soil
(µg/kg)

Comparison
Value for
Ingestion
(µg/kg)*

Range in
Groundwater
(µg/l)

Comparison
Value for
Ingestion (µg/l)*

Comparison
Value Source*

1,2-Dichloroethane

ND

8,000

ND-27

0.4

CREG

1,1-dichloroethylene

ND

1,000

ND-527

0.06

CREG

Trans-1,2-dichloroethylene

ND

40,000

ND-201

200

RMEG

Tetrachloroethylene

ND

10,000

ND-18

0.7

CREG

1,1,1-Trichloroethane

ND

11,000

ND-2,439

200

LTHA

1,1,2-Trichloroethane

ND

10,000

ND2-11

0.6

CREG

Trichloroethylene

ND

60,000

ND-4,500

3

CREG

Polychlorinated Biphenyls

ND-103,800

90

ND**

0.005

CREG

* - See
Appendix 2 for a description of the comparison values and their sources.1 - ND is nondetect.µg/kg - micrograms of contaminant per kilogram of soilµg/l - micrograms of contaminant per liter of water** - Only one groundwater sample was analyzed for polychlorinated biphenyls.
The bold indicates those contaminants whose concentrations are above the comparison value.

* - See Appendix 2
for a description of the comparison values and their sources.1 - ND is nondetect and NA is not analyzed. µg/l - micrograms of contaminant per liter of water** - Only one sample was analyzed for polychlorinated biphenyls.
The bold indicates those contaminants whose concentrations are above the comparison value.

The groundwater monitoring data indicate that the contamination originating from Potter
Company migrated into the Wesson Municipal drinking water well numbers 1 and 2 (6). TCE
was first detected in these wells in August 1987 (5). Table 3 lists the contaminants detected
above health comparison values in the Wesson Municipal Well number 1, Well number 2, and
the distribution system.

The concentrations of contaminants in the distribution system were significantly reduced when
the aerator at the Wesson water treatment plant was modified in May 1988 (5). Analytical results
of samples taken after the modification indicate that TCE concentration fell to about 14 µg/l.
After the new wells (Well numbers 3 and 4) were connected and the old wells (Well numbers 1
and 2) were closed (June 1989), the TCE concentration in the Wesson Municipal Drinking water
distribution system was below detection limits (less than 0.5 µg/l).

The State of Mississippi identified and sampled all of the active residential drinking water wells
in the Wesson area (13). Analytical results of these samples indicate that only one residential
well was contaminated with TCE. This well is located northwest of the proposed Potter
Company NPL site. ATSDR was told that this well is no longer used for drinking water and that
the residence associated with this well was connected to the Wesson drinking water distribution
system.

In addition to sampling the active residential drinking water wells, the State of Mississippi also
sampled the spring the City of Wesson previously used as its only source for drinking water
(1922 to 1974) (5). Analytical results of this sample indicate that the spring was not
contaminated with TCE.

Only one groundwater sample taken from a monitoring well (MW-37) was analyzed for PCBs
(10). The results of this analysis indicates PCBs were not present in the groundwater at that
location and time (1988). The State of Mississippi checked for the presence of PCBs in Wesson
well numbers 1 and 2 in 1988 (5). These one time sampling results indicate PCBs were not
present. Additional sampling from the areas of higher groundwater contamination is needed to
confirm that PCBs have not migrated into the groundwater and off-site.

ATSDR was able to obtain quality assurance and quality control (QA/QC) information for most
of the data presented in this Public Health Assessment. This information indicates appropriate
QA/QC was performed for the samples. The conclusions presented in this Public Health
Assessment are based in part on the data presented. The validity of the conclusions, therefore,
depends on the accuracy and reliability of the data provided.

To identify possible facilities that could contribute to the environmental contamination in
Wesson, ATSDR searched the 1987-1991 files of the Toxic Chemical Release Inventory (TRI)
databases for Copiah and Lincoln Counties. TRI was developed by the EPA from chemical
release (air, water, and soil) information provided by certain industries.

Several limitations of TRI data should be noted (14). The air release data in TRI may be
estimates or actual measurements. Many of the reported data are estimates based on conservative
(overestimated) scenarios. Consequently, the levels of emissions recorded in TRI are often
biased on the high side. In addition, reporting is restricted to specific chemicals that are used or
released above specified amounts. Finally, it is believed there have been and still are industries
that do not report releases. Smaller industries may not be aware that reporting requirements exist
or that they are responsible for such reports.

The search of TRI did not identify any facilities that could have contributed to the contamination
in Wesson (15).

PATHWAYS ANALYSES

In this section of the Public Health Assessment, the possible environmental pathways are
evaluated to help determine whether individuals have, are, or will be exposed to site-related
contaminants. Environmental pathways can be completed or potential. A completed pathway
indicates that human exposure to contaminants has occurred in the past, is occurring, or will
occur in the future (16). A potential exposure pathway indicates that human exposure to
contaminants could have occurred in the past, could be occurring, or could occur in the future.
An exposure pathway can be eliminated from consideration if exposure has and never will occur.
If there is uncertainty about the site-relatedness of the contaminants of concern in an exposure
pathway, the pathway will be evaluated as if the contaminants were site-related.

The completed and potential environmental exposure pathways, as well as those for which there
is no known exposure, are discussed below.

Table 4 lists the components of the groundwater environmental exposure pathway which is
considered the only completed (i.e., human exposure has occurred or is occurring) and the
estimated number of individuals in this pathway.

There is good evidence that humans were exposed (ingestion, inhalation, and skin contact) in the
past to site-related contaminants via the Wesson municipal drinking water distribution system
(6). Analytical results of environmental samples taken from the local groundwater aquifers
indicates that TCE, TCA, and the biological breakdown products of TCE and TCA have
migrated into the three layers of the local groundwater aquifer. The City of Wesson well
numbers 1 and 2 tap these aquifers (5). Analytical results of samples taken from Wesson well numbers 1 and 2 show that TCE, TCA, 1,1-dichloroethylene, and total
1,2-dichloroethylene have migrated into the wells. Drinking water samples were taken from the
Wesson municipal drinking water distribution system. Analytical results of these samples
confirm that TCE, 1,1-dichloroethylene, and total 1,2-dichloroethylene were in the water drunk
by the citizens of Wesson from September 1987 through June 1989. The contaminated wells
were replaced with uncontaminated wells (Wesson well numbers 3 and 4) in June 1989.

No information is presently available to indicate when the Wesson wells became contaminated.
The City of Wesson started to use well number 1 in 1974.(1) Prior to 1974, drinking water came
from a spring; however analytical results of a sample taken from the spring indicates that this
source of drinking water was not contaminated. Therefore, it is not likely humans were exposed
to site-related contaminants (i.e., TCE, 1,1-dichloroethylene, and total 1,2-dichloroethylene)
prior to 1974.

In order to determine how long Wesson well numbers 1 and 2 were contaminated, one would
have to model the groundwater system. ATSDR will try to model the groundwater system in the
near future. For the purpose of this assessment, ATSDR will assume the worse case situation,
the wells were contaminated from 1974-1989 (15 years).

The 1980 U.S. Census indicates the City of Wesson had a population of 1,313 (2). All of these
individuals received their drinking water from the Wesson municipal drinking water distribution
system. In addition to the city residences, students at the Copiah-Lincoln Community College
(approximately 1,000 students) also received their drinking water from the Wesson municipal
drinking water distribution system. Therefore, the exposed population for this proposed NPL site
is approximately 2,300.

There are no other completed environmental exposure pathways related to the proposed Potter
Company NPL site.

Table 5 lists the components of the four environmental exposure pathways considered to be
potential, and the estimated number of individuals in each pathway. These possible
environmental exposure pathways are surface and subsurface soil, future migration of the
contaminated groundwater into drinking water wells, worker exposures during degreasing
operations and waste material handling, and air.

1. Surface and Subsurface Soil

Analytical results of surface and subsurface soil samples indicate wide spread PCB
contamination (1). The PCB (primarily Aroclor 1254) soil contamination was found on the
Potter Company property, the Byrd property, and in the unnamed stream off the Potter property.
By 1993, all of the PCB soil contamination greater than ten ppm at the Potter Company property
and greater than one ppm at the Byrd property or in the unnamed stream was removed by the
remedial activities conducted by Potter Company. Therefore, humans were possibly exposed to
the PCB soil contamination from 1953 (the start of Potter Company activities at this location) to
1993.

Individuals, primarily children, could have been exposed in the past to the surface and subsurface
soil PCB contamination via inadvertent consumption and skin contact with the soil on hands or
food items, mouthing of objects, or the ingestion of nonfood items (pica). In addition, these
individuals could have inhaled the soil contaminants whenever the surface and subsurface soil
were disturbed (e.g., dust and particulate matter). All children mouth or ingest non-food items to
some extent. The degree of pica behavior varies widely in the population, and is influenced by
nutritional status and the quality of care and supervision. Groups that are at increased risk for
pica behavior are children aged 1-3 years old, children from families of low socioeconomic
status, and children with neurologic disorders (e.g., brain-damage, epilepsy, mental retardation).
Because of the inadvertent nature of this possible exposure pathway, it is not possible to estimate
the number of exposed individuals.

Because of the remedial actions conducted by the Potter Company, it is unlikely individuals will
be exposure to PCB contaminated soil currently and in the future at or near the proposed Potter
Company NPL site.

Although not contaminated now, four public drinking water wells appear to be in the direct path
of the groundwater contamination. The Wesson well numbers 4 and 5 and the Lincoln Rural
Water Association well numbers 1 and 2 are approximately one mile east and southeast of the
leading edge of the groundwater contamination (see Appendix 1, Figure 3). If the groundwater
contamination continues to move east/southeast, these wells could possibly become
contaminated. Individuals who rely upon these wells for drinking water could then be exposed
(ingestion, inhalation, and skin contact) to site-related contaminants (e.g., TCE). However, the
Mississippi Bureau of Pollution Control has approved Potter Company's plan for groundwater
remediation system. The remediation system should become operational in the first quarter of
1995. The goal of this system is to prevent future migration of contaminated groundwater.

Because this exposure could possibly occur in the future, the size of the exposed population can
not be estimated.

3. Worker Exposure

When material was degreased and the waste fluids from the degreasing operations were dumped
onto the ground, Potter Company employees could have been exposed (ingestion, inhalation, and
skin contact) in the past to TCE, TCA, and PCB. In addition to the potential past exposures,
Potter Company employees could be presently or in the future exposed to TCA during
degreasing operations and waste fluid disposal (currently the waste fluids are reportedly disposed
of in accordance with hazardous waste regulations). The extent of exposure would depend upon
what personal protection equipment the workers wore (i.e., gloves, protective clothing, and
respirator) and the length of contact, both of which would affect the amount of waste material
ingested, inhaled, or accumulated on the skin. Less than ten employees are involved with
degreasing operations and disposal of the waste fluids.

4. Air

TCE and TCA could have volatilized into the air and migrated off the Potter Company property.
Individuals not employed at Potter could inhale (past, current, future) the TCE or TCA. The
distance to the nearest residence is less than 150 feet away (the Byrd residence). Therefore, it is
possible that some TCE or TCA discharged to the air from the degreasing operation could have
migrated off-site. Because air monitoring data is not available, it is not possible to confirm or
deny whether humans could have come in contact with TCE or TCA via air emissions.

Analytical results of samples taken from the Wesson and the Lincoln Rural Water Association
drinking water distribution systems indicate there is no site-related contamination. Therefore,
there is currently no exposure to site-related contaminants via drinking water.

PCBs are known to bioaccumulate in plants and animals (9). However, there is no evidence that
PCB contaminated soil or water was used to raise food stuff. In addition, fishing is not
conducted in the stream where PCB contamination occurred (the stream is frequently dry).
Therefore, it is unlikely individuals would be exposed to PCB via food.

As discussed in the Pathways Analyses section, the Wesson Municipal Drinking Water Supply
exposure pathway is considered completed (i.e., human exposure occurred). The contaminants
of concern in this pathway are trichloroethylene (TCE), and 1,1-dichloroethylene.

The Toxicological Evaluation portion of this section will discuss the possible health hazard from
past exposure to the two contaminants of concern in the Wesson Municipal Drinking Water
Supply. The community's concern about cancer will be addressed in the Health Outcome Data
Evaluation section which describes cancer mortality data.

Typically, the toxicological evaluation in a public health assessment is a comparison of the
exposure dose (i.e., the amount of a substance individuals in an exposure pathway are exposed to
daily) to an appropriate health guideline. In this evaluation, the health guidelines are ATSDR's
Minimal Risk Levels (MRLs). The results of the comparison of the exposure doses to the MRLs
for each chemical is described in Table 6, and the methodology for calculating the exposure
doses in Appendix 3.

Neither the adult, nor the child exposure doses for the maximum levels of 1,1-dichloroethylene (1
µg/l) and TCE (219 µg/l) in the Wesson Municipal Water Supply exposure pathway exceed the
MRLs for those chemicals. Usually, any exposure dose below the appropriate MRL does not
represent a hazard to human health (16). However, the only available health guideline for TCE
is for an exposure of less than a year. There is some indication from recent studies that health
effects from exposures of more than a year might occur at the TCE levels found in the Wesson
Municipal Water Supply. Because of this, the possible health consequences of exposure to TCE
will be discussed.

TCE is considered a probable human carcinogen and 1,1-dichloroethylene a possible human
carcinogen (17). The risks of carcinogenic health effects from 1,1-dichloroethylene and TCE exposure were evaluated using the methods described in
Appendix 4. Based on this evaluation,
the past exposure to 1,1-dichloroethylene in the Wesson Municipal Water Supply System
represents no apparent increased risk of cancer. There was a low increased risk of cancer from
past exposures to TCE.

1 - An explanation of how
exposure doses are calculated can be found in Appendix 3.
2 - IMRL is intermediate minimal risk level.
3 - CMRL is chronic minimal risk level.

Discussion of Possible Health Consequences

The possible health consequences of exposure to TCE are described in the following paragraphs.

Health assessors determine the possibility of health consequences by comparing the exposure to
the results of epidemiologic evaluations of human exposures to a chemical. If valid human data
are not available then information from properly conducted animal studies are used. The type of
data used for an evaluation is indicated for each chemical.

Trichloroethylene (TCE)

Noncarcinogenic Health Effects

Based on studies of workers and laboratory animals, the exposure to TCE in the Wesson water
supply does not appear to be of a high enough concentration to result in noncarcinogenic health
effects (11). However, several recent studies of individuals exposed to TCE in drinking water
identified several health effects which had rates greater than comparison groups (18-23). The
health effects reported in those studies were stroke and impaired hearing (18); slowed eye blink
response (19,20); several abnormal neurophysiological and neuropsychological parameters (20);
impairment of the immune system (21); increased occurrence of the symptoms related to lupus
(22); and congenital cardiac malformations (23).

Elevated rates for several health outcomes were found in participants in the TCE exposure
registry when compared with respondents to the National Health Interview Survey (18). These
outcomes included (for various age and sex groups) speech impairments, hearing impairments,
hypertension, stroke, liver problems, anemia and other blood disorders, diabetes, kidney disease.
urinary tract disorders, heart conditions, and skin rashes. Only the rates for strokes and impaired
hearing were related to the concentration of TCE. The approximately 4,300 participants in this
registry were exposed to 2 to 19,380 ppb in drinking water for up to 18 years. These results are
limited by the lack of confirmation of the health conditions and less than complete identification
of exposure levels. The results do not establish a cause-and-effect relationship between exposure
and adverse health outcomes.

Significantly slower eye blink responses were identified in TCE-exposed individuals from
Woburn, Massachusetts and Tucson, Arizona (19,20). Those slower responses were considered a
subclinical effect (i.e., not harmful). The validity of these results is limited by the non-random
selection of the participants and the lack of a identification of a dose-response relationship. In
addition, a recent study of workers exposed for an average of 16 years to many times the TCE
concentrations found in Arizona and Massachusetts found no change in the eye blink response
(24).

Impairment of the immune system was observed in TCE-exposed individuals from Woburn,
Massachusetts (21). This immunologic impairment was evidenced by altered T-cell ratios
(T-cells are a type of white blood cell), increased incidence of auto-antibodies, increased
infections, and recurrent rashes. The validity of these results is limited by the non-random
selection of the participants (they were all relatives of children who had leukemia) and the lack
of a identification of a dose-response relationship.

Increased occurrence of the ten symptoms used to diagnose lupus was identified in TCE-exposed
individuals from Tucson, Arizona (22). The validity of these results is limited by the
non-random selection of the participants and the lack of a identification of a dose-response
relationship.

Another study of the TCE-contamination in Tucson found that the rate of total congenital cardiac
malformations was higher in the area where TCE-contaminated water was probably ingested
compared to areas without TCE-contamination. These results are limited by uncertainty about
the extent of the contamination and the lack of exposure information to evaluate a dose-response
relationship.

The results of the studies reviewed indicate that further investigation of low dose TCE exposures
is needed. However, they do not offer any evidence about a cause-effect relationship between
TCE exposure and specific health effects. Thus they do not offer any assistance in interpreting
the possibility of health consequences from the exposure to TCE in the Wesson water supply.

Carcinogenic Health Effects

The levels of TCE found in the Wesson Municipal Water Supply represent a low increased risk
of cancer. However, there is a great deal of uncertainty about the carcinogenicity of TCE.
Studies of workers exposed to TCE did not identify an increase of cancer (11). Investigations of
exposures to TCE in drinking water from Woburn, Massachusetts and several New Jersey
communities suggest increases of leukemia. However, both studies have numerous
methodological problems. Evaluations of the series of animal studies vary from a determination
of TCE as probable human carcinogen by EPA to "not classifiable for cancer" determinations by
the International Agency for Research on Cancer. An evaluation of cancer data for the City of
Wesson would help address this uncertainty.

B. Health Outcome Data Evaluation

We evaluated cancer mortality data for Copiah County. The number of deaths due cancer in
Copiah County was not greater for the 14 anatomical sites or combination of anatomical sites
evaluated than what would be expected from the numbers for the State of Mississippi. Cancer
data were evaluated because they were identified as biologically plausible health outcomes.

For biological plausibility, the decision to evaluate health outcome data depends on whether a
completed exposure pathway exists for a chemical suspected of causing the health outcome of
concern (16). The selection of a noncarcinogenic health outcome is based on a review of the
toxicologic literature for that contaminant of concern.

When a contaminant of concern has been identified as a carcinogen, health outcomes for the
major anatomical sites are usually selected for evaluation (16). Designating a chemical as a
carcinogen (for purposes of health outcome data evaluation) is based on classification as such by
the National Toxicology Program (NTP), the International Agency for Research on Cancer
(IARC), the United States Environmental Protection Agency (EPA), and the United States
Occupational Safety and Health Agency (OSHA).

A latency period of at least 10 years between exposure and diagnosis has been observed in most
studies of human cancer (16). If exposure began less than 10 years prior to the latest data
available, analysis of health outcome data for cancer incidence or mortality is not likely to be
useful, particularly if the exposure level is low.

Even when health outcomes do not meet ATSDR's guidelines for biological plausibility, health
outcome data can be evaluated to address community health concerns.

For the proposed Potter Company NPL site, cancer is considered a biologically plausible health
outcome because: trichloroethylene (TCE) is considered a probable human carcinogen (11), and
people were exposed (i.e., they were in a completed exposure pathway) to this contaminant in the
Wesson Municipal Water Supply for up to 15 years. Cancer mortality data were available and
were evaluated. Cancer incidence data were not evaluated in this public health assessment
because the State of Mississippi does not have a Cancer Incidence Registry.

Developmental or birth defects were not considered biologically plausible health outcomes.
Neither TCE and 1,1-dichloroethylene are strongly associated to those effects (11,25).

Cancer Mortality Data

To identify cancer mortality rates, ATSDR reviewed mortality data on 14 anatomical sites or
combination of anatomical sites for Copiah County for 1979-1991. Those data came from a
database maintained by the Office of Analysis and Epidemiology of the National Center for
Health Statistics, Centers for Disease Control and Prevention. The anatomical sites evaluated
were lung; lip, mouth, and throat; digestive tract and pancreas; liver and gall bladder; bone,
connective and soft tissue; skin; breast; female reproductive; male reproductive; bladder and
kidney; lymphatic; leukemia; all other sites; and all sites combined. Information specific to the
City of Wesson area was not available.

The age-adjusted rates for Copiah County were compared to the rate for Mississippi. Because
Copiah is split evenly between African-Americans and Whites, comparisons were made for both
groups.

The number of deaths due cancer in Copiah County was not greater for the 14 anatomical sites or
combination of anatomical sites evaluated than what would be expected from the numbers for the
State of Mississippi.

Evaluations of cancer mortality data have limitations. A major limitation is that the data
evaluated were for Copiah County, not the City of Wesson. The population of Wesson (1,313)
makes up about 5% of the population of Copiah County (26,952). Because of this disparity,
effects on the population of Wesson may not identified. An evaluation of cancer mortality data
for just Wesson needs to be done to eliminate this limitation.

Another limitation is that the cancer mortality data used did not include information on personal
risk factors (smoking, diet, alcohol, etc.) or on occupational and environmental exposures to
chemicals. Analyses of those data can only be descriptive and cannot be used to determine
associations with possible agents. There is an inherent five percent chance that any excess in
observed cancer cases is due to random variation alone.

A third limitation is whether mortality data reflect the actual frequency of a disease (i.e., deaths
plus those who survive) (26). Factors such as quality of health care, high survival rates, and
misclassification of cause of death can lead to differences in mortality rates even though the true
frequency of the disease has not changed.

C. Community Health Concerns Evaluation

The one identified community health concern, "Is the rate of cancer in Wesson elevated?", can
not be fully addressed. Only county-wide cancer mortality were available for evaluation. This
evaluation is described in the preceding section, and, as discussed, a review of data for Wesson is
needed to fully address this concern about elevated cancer rates.